1. Field of the Invention
This invention is related to image scanners and, more particularly, to a scanning area detection method for use with a shuttle scanner which utilizes a document-size detection sensor mounted on a paper guide to reduce data transmission time and improve image output quality.
2. Discussion of Related Art
In the case of a general-purpose image scanner, such as that used in a typical facsimile machine which uses a white roller or white bar as a background and spans the entire mechanically available area (width) for scanning, all points other than the actual image data are processed as "white" data, i.e. , blank. Accordingly, any area lying outside that of the document original is scanned as white and is thereafter processed as white data at the time of reproduction (e.g., printing).
Meanwhile, with the aid of graphics software, a user-selectable scanning area is made possible, so that specified areas can be scanned and the captured data processed. For example, a pre-scanning function is used to set precisely the area to be scanned, wherein low-resolution, rapid scanning is first performed over a large area in order to catch the general shape of an image to be scanned, with the captured data being displayed the monitor of a computer system for more precise scanning of a specific area.
While neither of the above scanning systems is a matter for concern since non-document areas can be processed as white data, in the case of a shuttle scanner module, which is the technique most often employed in a multifunction machine such as a printer/scanner, a unique problem arises. That is, in using the typical shuttle scanner, the travel of the scanner module is determined by the maximum allowable width of the scanning medium, e.g., paper, so that any area beyond the width a given sheet of paper is also scanned and processed. This extra-document data is unavoidably captured and is usually processed as black (or nearly black) data. Therefore, since a sizable portion of the left or right side of the reproduced results is ultimately printed as a virtually all black image, the consumption of ink or toner is excessive. Furthermore, under such printing conditions, print quality is diminished and is unsightly in general.
In particular, these phenomena create undesirable conditions and unfavorable results during facsimile transmission and especially at the point of facsimile reception. Moreover, data transmission time is unnecessarily long.